Just do it correctly. Get a 30$ temp switch from summit. An adapter from eBay for 8$ and put it in the top rad hose so at a certain temp the probe will send voltage to a relay turning the fans on and off. You won't ever have to worry about it that way


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I have Altima fans in my car. I wired each fan to the battery with a relay and 30AMP fuse. Then I used a thermostatic switch (fused as well) to turn the fans ON. So I have one thermostatic switch (prong in radiator), 3 relays and 3 fuses. Super safe. I spent more money on the relays and wires than the fans. FYI

My car isn't a daily and only on the track so I jumped high and low speed together to turn on with the switch. Works awesome. You could wire low speed if you wanted, but its a waste in my opinion. The HIGH speed cools the temps quickly and I beat the crap out of it at the track with no high temps.

Just make sure you buy a quality thermoswitch. I had one from Pep Boys for $30 and I had to replace it two times before getting a good one. Now my LS1 ECU turns the fans on

i dont want to burn out the motors, and i understand that if both sets of wires are energized then you get a medium speed instead of the full high.

This is news to me. I have the speeds wired together (12V to both HIGH and LOW) and it has been working fine for me.....I didn't think HIGH would activate unless LOW had a 12V signal as well. Could you cite where you found this info?

 

so i did some reading...

with 5 pin relays, i could use terminal 87a on high speed relay to feed terminal 86 on low speed relay and then install my thermoswitch in that line, which would send current to the low speed when high is not engaged, but then when high is engaged would disconnect the switch for the low speed. assuming i am reading this right, i would essentially be making my own fan controller for a 185 low and a 210 high, with high also coming on with the a/c compressor. hooking up in this manner there would be no way to have low and high trying to run at the same time.

i got a thermoswitch from an accord. it is a 180-185 degree switch. and i would trust an oem type switch in a bung more than a probe in a radiator fin or hose.. which is why i am not trying to put the thermoswitch in right now. i have to get some way to install the switch. was gunna have a bung welded in the water neck but i may get one of those hose adapters.

 

so i did some reading...

with 5 pin relays, i could use terminal 87a on high speed relay to feed terminal 86 on low speed relay and then install my thermoswitch in that line, which would send current to the low speed when high is not engaged, but then when high is engaged would disconnect the switch for the low speed. assuming i am reading this right, i would essentially be making my own fan controller for a 185 low and a 210 high, with high also coming on with the a/c compressor. hooking up in this manner there would be no way to have low and high trying to run at the same time.

NEGATIVE. For HIGH to work, LOW needs signal. I'm 99.99% sure.

 

I found this:

One Fuse and One Relay for One Fan. My thermostatic switch is fused and relayed as well, but duplicate this for each fan. If you don't want them to turn on together just run the BLUE / GREEN wires to different activators.

 

i keep hearing conflicting info on this point. guess i need to do some testing. if that is the case then it simplifies my wiring a bit.

 

Agreed. I have it wired like the above. Both 12V to LOW and HIGH circuit, and it has been working great for about a year. Again the car does not get daily driven so the mileage is a whole lot less. Do you have the fans yet? I'm in the middle of a build and my fan is off so I could test it really easily.

Would you want me to confirm if the fans turn on when I send signal to only the HIGH circuit?

 

i have the fans, and know they turn on with just 2 wires, but not sure what happens with all 4.

guess i will go pull out the jumper cables and find out. thanks for the help and offer though!

 

i tested the fans again. either set of wires alone seems to be low speed. all together is faster, so if i don't have the low on already, then when the high kicks in it will just be low.

i got the extension dongles with the fans, so i will be able to remove/replace fans without rewiring. so my wire colors are

black and white/red - grounds
white/blue and white/black - powers

so, do i need 4 relays or should 3 be fine? i have seen writeups with 2-3.

was looking at this thread for wiring,
http://www.ka-t.org/forums/viewtopic.php?t=53033&sid=49bd34903f462deb37cfa6b7cbef1853
and i am not quite sure what is going on with the relays and how they are hooked together. but it looks like what i want to do except no controller, i would get the high sig from the factory wiring for the a/c fan, and the low from a acc switch for the time being, and add a thermoswitch at some point. so what i dont understand is why the relays are attached together and why the power to the fans is one high and one low, the other relay is only high ground?

 

my original thought was that i would use 2 for the highs, and 1 for the low, but i am not sure now...

i think is is kicking the low on if not already on by connecting the 87a pin but that wouldnt be needed if the low was going to be on already.

if the high is on and the thermoswitch isnt turning on the low, then power would be conserved if the car wasnt hot enough to need it. and if it did heat up then the low would kick in and high would happen, it would be like a double high/low setup where either could trigger low, but it took both to trigger the high speed. in this case only 2 relays should be needed, unless i wanted a 3rd trigger.

not sure if there would be a point, but it should be possible to run one fan always on low, one thermoswitched low, and both with a high trigger. that would keep a maintenance airflow and be able to stage it to come on in 4 different steps:
1 - low - off
2 - low - low
3 - high - low
4 - high - high

also only putting extra wear load on one fan.

 

okay. i did the last thing i said...

both fans to a relay triggered by the ecu/air cond (factory wires)
1 fan triggered by relay from the fuel pump fuse
1 fan to be triggered by a relay connected to a 180* thermoswitch

so i willhave a constant low on pass side fan
and the ac switch or ecu 210* trigger will switch on both fans
the driver side fan will be able to be switched on by a thermoswitch

so i will have 4 stages of fan cooling once i get the thermoswitch installed. but right now only 2. but the 2 should be more than the factory fan system ever was.

it is kinda a mess of wires. i ran a large power and extended both the factory wires, as well as a trigger wire fron the fusebox behind the battery. put all that in a wire loom that i mounted under the rad support with zipties to the factory harness that already goes through there. on other side where the charcoal canister is normally i have a bracket with 3 relays. 1 triggered by factory fan wires, one by fuel pump fuse and one by a thermoswitch that i have not installed yet. those go to their respective grounds and fans. then i had cut part of the fan harness with the altima fans and i wired them to the relays and grounds. so now i can also remove fans and not have to rewire. can take pics if anyone wants.